Until Martin Pomper and his team engineered a new radioactive compound to light up prostate cancer cells on PET scans, it was hard to be sure that patients were cancer-free after treatment. Pharmaceutical manufacturer Progenics recently licensed the breakthrough imaging agent, which is currently in clinical trials.

Prostate cancer, the second most common lethal cancer in American men, is also among the hardest to see. Buried deep behind the bladder, the prostate appears on X-rays and PET scans as a ghostly, oblong shadow. Even metastases due to the disease are elusive with conventional imaging methods.

The radiopharmaceutical is designed to help urologists keep an eye on patients whose prostate cancer doesn’t yet warrant treatment and those who are at a high risk of developing metastatic disease. Because the entire gland—or body—is imaged at once, it offers a more complete picture of prostate cancer than a biopsy.

“We can spot lesions as small as 2 to 3 millimeters,” says Pomper, a radiologist.

Patients in early tests have tolerated the radiopharmaceutical well. In addition to better-quality images, because of substantial optimization of its molecular structure, it is more specific than standard imaging methods, such as CT and bone scans.

Pomper points to a patient whose prostate-specific antigen levels were slightly elevated following removal of the prostate, indicating that the surgery didn’t catch all the cancer cells. Before Pomper’s new radiopharmaceutical, the treatment would have been to irradiate the patient’s pelvic region in hopes of knocking out the stray cancer cells.

“But it turned out that the cancer spread up near the aorta,” says Pomper. “That radiation would have been ineffective against the cancer. The fact that we could see where the cancer spread completely changed the direction of treatment for that patient.”

Pomper predicts the radiopharmaceutical will become a commercial product within three or four years.